5/17/12

Course Over-view

Click to edit Master subtitle style Lecture by M.Rafiq Afridi

Preston University

5/17/12

Introduction


In 1896, Gugliemo Marconi invented the wireless telegraph. 1901, he sent telegraphic signal across the Atlantic ocean from corn wall to Newfoundland. A distance of about 3200km. the last century, advances in wireless technology have let to radio, TV, mobile phones and communications satellite. The first communication satellite was launched in 1960.

 In

 Over

5/17/12

Transmission Fundamentals
 Analog

signal is a continuous signal that changes in a smooth way. It might represent data. signal is a signal whose only two states are available, +ve & -ve. It might represent 1s and 0s. signal in which the same wave signal pattern repeats over time. A periodic analog signal is called sine wave and a digital signal is called square wave.

 Digital

 Periodic

 Frequency
 Phase
. is the measure relative position in time within a signal period of a signal. is the ratio of in cycles per second hertz (Hz) at which the signal repeats.5/17/12
Transmission Fundamentals
 Peak
amplitude it is the maximum value or strength of the signal over time.

 Encoding

. where v is velocity and t is time period. is the conversion of signal from analog to digital. Its is represented by λ.5/17/12
Transmission Fundamentals
 Wavelength
of a signal is the distance covered by a signal to complete one cycle. Decoding is the conversion of signal from digital to analog. λ = v × t.

5/17/12
Transmission Fundamentals
 Modem
is a modulator and a de-modulator.
.
 Channel
capacity is at which data can be transferred in a channel.

copper coaxial cable. the atmosphere and outer space are the example. This form of transmission is usually referred to a wireless communication. media it provides a means of transmitting electromagnetic signal but do not guide them.
 Guided
 Un-guided
. optical fiber. such as copper twisted pair. media is the waves are guided along a solid medium. It can be classified as guided media and un-guided media.5/17/12
Transmission Media
 Transmission
media is the physical path between transmitter and receiver.

.5/17/12
Multiplexing
 Different
inputs or signals that can be transmitted through a single medium is called multiplexing.

corresponding multiplexor.
A
 The
A
. all signals are transmitted at the same time. Thus. or demultiplexor. each using different frequencies. multiplexor accepts inputs and assigns frequencies to each device.5/17/12
 Frequency
 Assignment
Division Multiplexing
of non-overlapping frequency ranges to each “user” or signal on a medium. multiplexor is attached to a high-speed communications line.

5/17/12
.

5/17/12

Time Division Multiplexing
of the signal is accomplished by dividing available transmission time on a medium among users. or asynchronous time division multiplexing. division multiplexing comes in two basic forms:
 
 Sharing
 Digital  Time
1. and 2.
. Synchronous time division multiplexing. signaling is used exclusively. Statistical.

5/17/12
.

Single link means point-to-point link.
Types of Connectons: there are two types of connections
1. Multidrop
.5/17/12
Communication Network
 Communication
network is the path between the sender and receiver through a medium with a feed back is called communication network. 2.

 Mesh  Star
Topology One node at the center as the master node.5/17/12
Types of topologies
 Bus
line. Network Topology mixture of star and ring topologies.
Topology Nodes are arranged in a single Topology Nodes are arranged in grids. Topology Nodes are arranged in a ring.
 Ring
 Hyper
.

5/17/12
Bus Topology
 It
is a network architecture in which a set of clients are connected via a shared communications line.
. called a bus.

5/17/12
Ring Topology
 Nodes  One
are arranged in a ring
node receives from its predecessor & sends to its successor
   
arbitrate who can access the ring messages forwarded by each node sender deletes its messages from the ring the common ring is the single point of failure (complicated connectors needed)
.

fiber optic cabling.5/17/12
Types of Networks
 LAN-
Local Area Network: Local Area Network a group of computers connected within a building or a campus (Example of LAN may consist of computers located on a single floor or a building or it might link all the computers in a small company. using different topologies such as telephone lines. Metropolitan Area Network: is a computer
 MAN-
.
 WAN-
Wide Area Network: A network consisting of computers of LAN's connected across a distance WAN can cover small to large distances. satellite transmissions and microwave transmissions.

5/17/12
OSI Model
 Open
Systems Interconnection (OSI) is a set of internationally recognized.
. non-proprietary standards for networking and for operating system involved in networking functions.

5/17/12
LAYER 7 – The APPLICATION Layer
 
The top layer of the OSI model Provides a set of interfaces for sending and receiving applications to gain access to and use network services. message handling and database query processing.
. such as: networked file transfer.

for incoming messages.LAYER 6 – The PRESENTATION Layer

5/17/12
Manages data-format information for networked communications (the network’s translator) For outgoing messages. it converts data into a generic format for network transmission. or data compression/decompression A special software facility called a “redirector” operates at this layer to determine if a request is network related on not and forward network-related requests to an appropriate network resource



. data encryption/decryption. it converts data from the generic network format to a format that the receiving application can understand This layer is also responsible for certain protocol conversions.

maintaining and terminating sessions Responsible for security and access control to session information (via session participant identification) Responsible for synchronization services.5/17/12
LAYER 5 – The SESSION Layer

Enables two networked resources to hold ongoing communications (called a session) across a network Applications on either end of the session are able to ex hange data for the duration of the session This layer is: Responsible for initiating.

 


. and for checkpoint services.

5/17/12
LAYER 4 – The TRANSPORT Layer
 
Manages the transmission of data across a network Manages the flow of data between parties by segmenting long data streams into smaller data chunks (based on allowed “packet” size for a given transmission medium) Reassembles chunks into their original sequence at the receiving end Provides acknowledgements of successful transmissions and requests resends for packets which arrive with errors


.

5/17/12
LAYER 3 – The NETWORK Layer

Handles addressing messages for delivery. as well as translating logical network addresses and names into their physical counterparts Responsible for deciding how to route transmissions between computers This layer also handles the decisions needed to get data from one point to the next point along a network path This layer also handles packet switching and network congestion control



.

this layer packages raw data from the physical layer into data frames for delivery to the Network layer. At the receiving end.5/17/12
LAYER 2 – The DATA LINK Layer

Handles special data frames (packets) between the Network layer and the Physical layer.


. At the sending end this layer handles conversion of data into raw formats that can be handled by the Physical Layer.

ex. etc. network interface cards (NICs.




. twisted pair. etc.5/17/12
LAYER 1 – The PHYSICAL Layer

Converts bits into electronic signals for outgoing messages Converts electronic signals into bits for incoming messages This layer manages the interface between the the computer and the network medium (coax.)) what needs to be sent across the medium The bottom layer of the OSI model.) This layer tells the driver software for the MAU (media attachment unit. modems.